A disc filter is for example used for filtration of water in purification plants. A common design of a disc filter comprises a rotating drum which is intended for receiving fluid which is to be filtered, and at least one disc shaped filter means which is provided outside the drum and which extends outwardly in the lateral direction of the drum. Fluid flows out through orifices in the drum and further through the filter means. Any particles in the fluid adhere to the filter means as the fluid passes through the filter means, and are hence separated from the fluid which passes freely through the filter means.
Known filter means comprise a filter frame and at least one filter section supported thereof. A filter section can be made in one piece, but this is often unpractical since the entire filter section has to be replaced if there is any damage, even if the damage is limited to a smaller area. Therefore, in order to facilitate maintenance and repair of damages, the filter section is usually divided into several separate filter segments, which together form one filter section and which are detachably attached to the filter frame. That way there is no need for replacing the entire filter section if any damage occurs, but only the filter segment which has been damaged, thus decreasing both costs and the amount of time needed for maintenance and repair.
The above described disc filter with detachably attached filter segments do in many cases work satisfactorily. But it appears that the filter frame becomes large and bulky as regards disc filters dimensioned for large flows. SE 526,692 describes a disc filter which partly amends this disadvantage since the filter frame is assembled by several modules which can be interconnected around the drum. The modules consist of a continuous intermediate member from which two outer members extend outwardly at one end, and two inner members extend outwardly at the other end. The inner members are intended for being attached at the drum and the intermediate member extends from the drum in radial direction. When two such modules are interconnected around a drum, they will together form a frame in which a filter segment can be attached. With this solution, where the filter frame consists of modules, the filter frame can be transported in disassembled form to the location, where the disc filter is to be used, and then assembled on location. Thus the disc filter device requires less space during transportation.
Even though the module system above exhibits many desirable qualities, there is still room for improvement. When the disc filter is dimensioned for very large flows the disc filter device according to the above, despite of the modular assembly, will be bulky during transportation and the transportation space has an upper limit as regards how large the delivered disc filters can be.